Q: How do I build a safe water rocket and that will go very high?

Schirra-1 Vehicle

A: The good news is that many of the design choices that will make the
rocket fly very high also make it safer. Here are a few design factors that will help:

Make the rocket using only light-weight plastic, cardboard, card-stock, or paper. A lighter rocket
with the same motor will fly higher. It's also safer because it will have less kinetic energy when it
lands so it will cause less damage to people or property.

Make the rocket as streamlined as possible. A well streamlined rocket has less drag, which means that
more of the energy will be translated into height rather than wasted in turbulent flows.

Make the rocket stable by increasing its length and moving the fins toward the rear. A stable rocket
will fly straight up, thus gaining a higher altitude.

Use the java simulation to pick the best Load Fraction for the size and weight of your rocket. Do a
little experimentation in the simulation "laboratory" to make your rocket fly highest.

Following this approach you should have a great performing rocket that will be safe to operate and a lot
of fun!